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Gardening: Cool spring perfect weather for aphids

This leaf has a bad infestation of aphids. The pale green and yellow aphids are surrounded by the frass left from molting nymphs.  (Courtesy Iowa State University Extension)
This leaf has a bad infestation of aphids. The pale green and yellow aphids are surrounded by the frass left from molting nymphs. (Courtesy Iowa State University Extension)
By Pat Munts For The Spokesman-Review

It’s been a great spring this year. Lots of rain and cool temperatures that have fostered lush growth, lots of long-lasting flowers and a hoard of aphid infestations. The WSU Master Gardener Plant Clinic reported they are seeing aphids on plants we normally don’t see them on. They even infested my tomato and pepper starts under my lights in March.

Aphids love tender leaves and buds on a lot of different plants. Because of the cool weather and extra rain, plants are growing double their normal size. That’s a lot of fodder for the pests. They are common on cole crop vegetables (cabbage, cauliflower and broccoli), tomatoes, peppers, eggplant and roses. The Master Gardeners are also seeing them on fruit trees, especially plums. Aphids are the most active in temperatures between 65 and 80 degrees, just like we’ve been having this year.

Aphids are sucking insects that feast on plant juices. Their feeding often distorts leaves and buds and eventually stunts the growth of the plant. Bad infestations can eventually kill a plant. Each adult can reproduce around 80 offspring in a week. The bugs are very small, pear-shaped and come in colors of green, yellow, brown, red or black depending on the species. The adults hide on the protective undersides of the leaves accompanied by frass from the molting nymphs. Under the right conditions a nymph can grow into an adult in less than 10 days, and there are many generations in a growing season.

So how do you get rid of them? First, catching infestations early and dealing with them is much easier than having to deal with a well-established population. So, start scouting your plants by turning over leaves on your garden walks. Most light infestations can be dislodged off the plants with a strong stream of water. Make sure you aim the jet to the underside of the leaves. Water jets like this are also a great way of controlling other insects like red spider mite on conifers later in the summer.

Learn to identify beneficial insects like lady beetle adults and larvae, lacewing larvae, soldier beetles, and syrphid fly larvae and scout for them. If present, these insects will appear shortly after the aphids and can keep light infestations under control. Another reason for not using broad spectrum insecticides.

If there is a bad infestation, it may be necessary to apply insecticidal soap, horticultural or neem oil sprays to smother the aphids. All are organic. Insecticidal soaps come in many brands and are available in most garden centers. Be sure to apply to the underside of the leaves.

Tip of the week: In this year we are hearing more about water conservation, I’d like to visit gardens that have taken on the challenge of reducing their water use. So, send me up to six pictures of your garden and its story and I will feature three of them between now and late September. Dig out your water bills from before and after to show your savings.

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